<div dir="ltr">Just a thought possibly for a low cost antenna system...<div><br></div><div>When I was a student many moons ago in Manchester, Radio Rag used to operate their AM transmitter from the student halls tower block I lived in. I don't know what you'd call it, but I guess it was an inverted monopole. 100W transmitter up on the 12th floor feeding into a near vertical wire radiator down to ground level.</div><div><br></div><div>Obviously if circularity in coverage is important that might be a problem (but I don't recall the signal was that strongly impacted behind the building). But if your local council are obliging it might be a way to get a reasonably efficient antenna quite cheaply.</div><div><br></div><div>Glyn</div><div><br></div><div>PS: Regarding the 3:1 argument I think the extra antenna efficiency/small size may well be offset (possibly more than offset) by the propagation advantage of the lower frequency. Laser did not choose 558kHz by accident.</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On 17 September 2015 at 18:44, Ian Hickling <span dir="ltr"><<a href="mailto:transplanfm@hotmail.com" target="_blank">transplanfm@hotmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div dir="ltr">If only it were as simple as that!<br>I must admit that I hadn't looked at it like that - <span style="font-family:sans-serif;font-size:14px;line-height:22.4px;background-color:rgb(255,255,255)">531 to 1,611 kHz gives a quarter wave range of of 141 metres to 46 metres - yes - three to one!</span><div><font face="sans-serif"><span style="font-size:14px;line-height:22.4px">But do you fancy buying/siting/building even a 46m guyed vertical radiator - 152 feet high?<br></span></font>Apparently there are only 9 AM frequencies that Ofcom feels able to allocate to LP operation - I'll see if I can find out what they are.<span class=""><br><br><div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8000001907349px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255)"><font size="3"><b>Ian Hickling</b><br></font></div><font style="color:rgb(34,34,34);font-family:arial,sans-serif;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);font-size:12pt" size="3"><font style="color:rgb(34,34,34);background-color:rgb(255,255,255)">Partner</font></font><br><br><a href="http://www.transplanuk.com/" style="color:rgb(17,85,204)" target="_blank"><img alt="" src="http://www.transplanuk.com/wp-content/uploads/2014/07/transplan_UK_weblogo_190x60.png"></a><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8000001907349px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><i><font size="3">Office: 01635 578435 (7am-11pm UK time)</font></i></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8000001907349px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><i><font size="3">Carphone: 07530 980115 (only responds when driving)</font></i></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8000001907349px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><i><font size="3">6 Horn Street, Compton, NEWBURY, RG20 6QS</font></i></div></div><br><br></span><div><hr>Date: Wed, 16 Sep 2015 21:28:28 +0100<br>From: <a href="mailto:tlr@gairloch.co.uk" target="_blank">tlr@gairloch.co.uk</a><span class=""><br>To: <a href="mailto:cma-l@mailman.commedia.org.uk" target="_blank">cma-l@mailman.commedia.org.uk</a><br>Subject: Re: [cma-l] AM community radio<br><br></span><div><div class="h5">
Given that the MF AM band covers a 3:1 frequency range, is Ofcom at least able to allocate a frequency at the high end of the band, making any given given aerial design a third the size it would be at the LF end of the band? Just wonderin'!<br><br><br><br>Alex<br><br><blockquote>On 16 September 2015 at 20:20 Ian Hickling <<a href="mailto:transplanfm@hotmail.com" target="_blank">transplanfm@hotmail.com</a>> wrote:<br><br><div dir="ltr">All perfectly acc<span style="font-size:12pt">eptable - but as an experienced propagation engineer my concern is that any departure from a vertical end-corrected quarter wave radiator operating on a groundplane of at least .55 wavelength diameter, the energy propagation pattern is uncertain and effectively impossible to either determine or plot.</span><div>In order to take his order - and his money - I have to give the Client an assurance that he will be able to cover his audience effectively - and that simply isn't possible with a cut-down compensated radiator on a much smaller earth mat.<br><br><div><div style="color:#222222;font-family:arial,sans-serif;font-size:12.8000001907349px;font-style:normal;font-variant:normal;font-weight:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:#ffffff"><span style="font-size:medium"><strong>Ian Hickling</strong><br></span></div><span style="color:#222222;font-family:arial,sans-serif;font-style:normal;font-variant:normal;font-weight:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:#ffffff;font-size:medium"><span style="color:#222222;background-color:#ffffff">Partner</span></span></div></div></div></blockquote>
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